Heretofore, medicaments for percutaneous administration were designed for topical actions on the epidermis or its subjacent tissue, such as pasteurization, sterilization, analgesic action, etc.
Recently, however, attempts have been made to administer medicaments having a systemic effect through the epidermis as well as by oral route and injection. Percutaneous administration of medicaments, particularly ones acting systemically is advantageous in that lasting of medicinal efficacies of the medicaments are facilitated; absorption rate of the medicaments is regulated so easily that side effects due to overdosing can be alleviated; the medicaments are so difficult to undergo the metabolism due to first-pass effect by the liver as seen upon oral administration that effective use of them is possible; even such medicaments that cause gastroenteric disorders by oral administration, e.g. indomethacin can be administered safely.
On the other hand, normal skin generally has, because of its effect of protecting the body, the properties of absorbing or permeating medicaments with difficulty. Consequently, even if medicaments (particularly, medicaments designed for systemic action) are administered in the form of ointments, lotions, etc. as usual, they are absorbed in the body with difficulty at least in an amount sufficient to exert medicinal benefits.
In view of the present situations discribed above, the present inventors have investigated intensively and obtained the following findings:
(1) A composition containing at least one compound (hereinafter may be termed generically adjuvant) selected from the group consisting of a saturated hydrocarbon containing 5 to 20 carbon atoms which may be substituted by halogen, an alcohol ester of aliphatic carboxylic acid containing 12 to 18 carbon atoms, an ether, a dimethylpolysiloxane having a viscosity at 25.degree. C. of not more than 6 centistokes and a cyclic polydimethylsiloxane having a viscosity at 25.degree. C. of not more than 6 centistokes; and an imidazolidinone derivative represented by the general formula: ##STR2## wherein R.sub.1 and R.sub.2 each are a lower alkyl enhances percutaneous absorbability of a medicament in the blood.
(2) The above-mentioned composition can be used as a base composition for medicament applicable to the epidermis. This invention has been accomplished on the basis of these findings.